The present invention relates to a valve shaft support structure, and more particularly, to a valve shaft support structure for a variable intake manifold, which can improve its durability, lower its manufacturing cost, and improve its quality, through forming of a valve shaft interposed between runners as a shaft integrally formed with a valve.
An intake manifold is a system of pipes which feeds air sucked through a throttle body into combustion chambers, and serves to uniformly distribute the air to the respective combustion chambers in a multi-cylinder internal combustion engine.
With the intake manifold, the engine efficiency is varied depending upon the length of a runner, through which the air passes. The length of the runner is preferably long if the engine is driven at a middle or low-speed range, while the length of the runner is preferably short if the engine is driven at a high-speed range.
As an alternative proposal, a variable induction system (VIS) which varies a length and a cross section of a runner in order to optimize a length and a cross section of an intake manifold depending upon an operation region of an engine has been developed and applied to the engine.
More specifically, a VIS variable intake manifold may improve the performance through the whole RPM range by opening or closing a valve of the intake manifold to effectively vary a length of the runner through various RPM ranges of an engine.
FIG. 1 is a view showing a flow of air produced when a valve of a conventional VIS intake manifold is opened or closed.
As shown in FIG. 1, when a valve 1 is opened, a flow of air is indicated by a line C1. While the valve 1 is closed, the flow of air is indicated by a line C2.
In the case where the valve 1 is opened, the flow path of air is short. By contrast, in the case where the valve 1 is closed, the flow path of air is long.
FIG. 2 is a view illustrating a conventional valve shaft support structure in the VIS intake manifold.
The valve shaft support structure 10 includes a shaft 11 and a bush 13 assembled to the shaft 11. The shaft 11 is interposed between runners is supported by the separate bush 13. Since there is no means for damping vibration generated when the engine is driven, the bush 13 supporting the valve shaft 11 and a valve screw (not shown) are released from a proper position. Also, undesired clearance or play may occur between the valve shaft 11 and the bush 13 due to wearing of the valve shaft and the bush, so that the valve shaft 11 becomes loose.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.